Magnetic clutch



Oct. 20, 1936. E, E, BERRY I 2,057,876

MAGNETIC CLUTCH Filed Dec. 21, 1931 Patented Oct. '20, 1936 MAGNETICCLUTCH Earl E. Berry, Belolt, Wis., assignor to Beloit Iron Works,Beloit, wa', a corporation of Wisconsin Application December 21, 1931,Serial No. 532,219

' 16 Claims. (Cl. 192-34) UNITED STATES PATENT OFFICE This inventionrelates to an improved magnetic clutch.

Magnetic clutches as heretofore designed and.

sult that the friction faces would wear unevenly.

The present invention, therefore, has for its principal object theprovision of a clutch in which special attention has been given both tothe electro-magnetic and the friction drive phases to avoid theaforesaid objections.

Magnetic clutches of one type in extensive use have 'a spring disccarrying the armature andarranged to-be deflected upon energization ofthe magnet to allow engagement of the clutch, and adapted thereafter toserve to disengage the clutch when the magnet would be deenergized. Adisc of this kind is an unsatisfactory mounting for the armaturebecause-a certain amount of distortion is bound to occur and destroy theuniformity of the air gap and accordingly make uniform and positiveengagement of the clutch out of the question. Such a construction is,furthermore, adapted only to the use of a single friction disc. Anothervery important object of the present invention, therefore, resides inthe substitution of compression springs for the spring disc forpositively disengaging the cluteh'by definite separation of the discsupon deenergization of the magnet; and the provision of an armatureslidable on a hub toward and away from the magnet and arranged toengages stop shoulder in its movement away from the magnet so as toinsure keeping a definite relationship between the magnet means forquickly and accurately measuring the a ap.

(2) The provision of fan blades in the back spider or flywheel of theclutch cooperating with registering holes in the driven discs andpressure plate, and exhaust 'holes behind the pressure plate, forventilation of the clutch as a whole and the compression springs inparticular to prevent overheating.

(3) The provision of openings in the rim of the flywheel adjacent theperipheries of the clutch discs permitting the escape from between thefaces of the driving and driven discs of any worn off material so thatthere may be uniform engagement of the clutch at all times. Also theprovision of a rim detachable from the flywheel so that the drivingdiscs, which are split diametrically, for assembly from the side of theclutch, may be removed for inspection or replacement withoutnecessitating disassembling of the clutch as a whole.

(4) The mounting of the driven elements of the clutch, including the hubcarrying the magnet, a front plate fixed thereto, and the armatureslidable with respect to the hub and operatively connected with thepressure plate, all as a unitary assembly on the driven shaft, the frontplate and pressure plate cooperating with one another to causefrictionalengagement therebetween of the driving and driven discs. This insuresparallel-. ism of the friction faces regardless of any slightdisalignment of the driving and driven shafts, so that the parts wearevenly. Furthermore, this insures smoother and more positive engagementof the clutch because with this assembly the force of attraction whichbecomes the force of engagementfor the clutch, isapplied in a directline from the armature to the pressure plate, exactly parallel with theaxis of rotation.

The foregoing and other features of the invention will be pointed out inthe course of the following detailed description, in which reference ismade to the accompanying drawing, wherein- Figure 1 is a centrallongitudinal section through my improved magnetic clutch, and

Figs. 2 and 3 are sectional details on the correspondingly numberedlines of Figure 1.

The clutch is illustrated in connection with a This bearing is arrangedto be lubricated through 5 a passage Ill provided in the hub of theflywheel. This afiords direct communication with the bearing for goodlubrication and eliminates the hazard that went with doing the greasingfrom the front of the clutch where the electrical equipment is located.A well known form of. pressure greasing nipple can be fitted directly inthe outer end of the pasage [0. A hub H keyed, as at l2, on the drivenshaft 6 has a front plate l3 bolted thereto, as appears at I4. 'The hubH is either splined or has gear teeth out in the periphery thereof, asindicated at 15, and carries thereon one or more driven discs iii inaddition to a pressure plate I1. These cooperate with the front plate l3to frictionally engage therebetween the driving discs I 8, which it willbe seen are re.- ceived in the intemal splines or gear teeth l9 formedin the ring 20, arranged to serve as the rim for the flywheel], beingbolted thereto as at 2|. The clutch illustrated is known as a tripledisc clutch because of its three driving discs l8, but it should beevident that one, two, or any other number of. discs could be used, andthat where one disc is used the discs l6 would be dispensed with, andthe driving disc would be engaged directly between the front plate I3and pressure 'plate I l. The driving and driven members are shown asarranged tohave direct metal to metal contact, but it will be evidentthat facings of suitable wear-resisting material could be provided oneither the driving or driven members. In the present case, since thedriving discs l8 are arranged to be removed for replacement, itwould beexpedient'to provide the facings on oppositesides thereof. Remo'val'andreplacement of the driving discs is made possible by having said discssplit diametrically as indicated at 22 in Fig.. 2 for assembly in theclutch from the side. By unfastening the ring 20 from the flywheel andmoving it rearwardly off the splined peripheries of. the driving discs,the discs'are exposedand may be easily removed for inspection andreplaced or others substituted. There is no need for disassembling theclutch or disturbing the connection with the prime mover or the machinedriven thereby. In passing, it will be observed that there are slots'2 3in the ring 20 between the discs l8. These slots permit the escape ofworn off friction material from between the driving and driven discs,the same being thrown out by centrifugal action. This is only one ofseveral factors, as willsoon appear, which account for the clutch discshaving smooth uniform engagement at all times.

coil 26 in an annular recess therein and held in place by a non-magneticring 21 set into the face.

of the magnet ring. An armature 28 is slidable relative to the hub lltoward and .away from the magnet 24. A collar 29 of brass or othernonmagnetic material is bolted onto the endof the net winding, wherebyto energize and deenergize the magnet accordingly as the circuit isclosed or' .The hub II has the magnet 24 mounted therei on, the sameconsisting of a ring 25 suitably pressed onto the hub and having amagnetizing opened. The armature 28 has an externally threaded rimportion 33 threading into the in-- temally threaded rim portion 34 ofthe pressure plate l1. It is therefore obvious that when the magnet 24is energized and the armature 28 attracted, the force of attraction istranslated into the force with which the pressure plate I! is movedtoward the front plate I3 for engagement therebetween of the drivingdiscs l8. That is to say, the pull of the magnet is reflected in thepressure exerted by the pressure plate I! for engagement of the clutch.A plurality of. coiled compression springs 35 are seated in recesses 36provided in equally circumferentially spaced relation in the opposingfaces of the front plate l3,v

driven discs l8, and pressure plate i1 respectively, and tend normallyto urge these driven members apart for disengagement of the clutch. Whenthe magnet 24 is energized, the clutch is engaged against the action ofthese springs. The fact that the armature 28 is guided for movement onthe same hub on which the magnet 23 is mounted insures uniformity of theair gap designated by the reference numeral 31, and also insures uniformdistribution of pressure on the driving discs by the pressure plate l1.In other words, the armature is guided in. its movement so that the facethereof remains absolutely parallel with the face of the magnet, andbeing so guided, it transmits aforce in a direct line parallelwith theaxis of the driven shaft to the pressure plate I'I, thus equallydistributing the pressure for engagement of the clutch. The front platel3, being also mounted on the hub II with its backvface in a plane atright angles to the axis of the driven shaft, and the pressure plate I!being guided for movement as just stated, through its connection withthe armature 28, and the pressure of engagement being equallydistributed, for the reasons stated, it follows that there will be notendency for the friction faces to wear unevenly and the same willremain substantially parallel. It should also be evident that the factthat the entire clutch with the exception of the driving discs i8 ismounted as a unitary assembly on the driven shaft, and the driving discsl8 fit loosely in the driving element, makes it possible to have slight-,d.isalignment between the driving and driven shafts without disturbingthe parallelism 'of' the friction faces. With the present constructionutilizing coiled compression springs35, instead of a spring disc, totake care of disengagement of. the clutch, I am enabled to provide anextremely practical clutch construction using more than one driving discand by doing this obtain many times the driving capacity while utilizinga magnet which, if anything, is weaker than those used with the otherconstructions, a saving in current consumption being accordinglyrealized. Further-v more; the utilization of coiled compression springsdisposed so as' to exert a force parallel with the axis of the drivenshaft and hence parallel with the sliding movement of the armature makesfor diameter being only slightly larger than that of the magnet itself.The advantagesof a clutch of small diameter are its greater adaptabilityand its low inertia factor. i

' as a whole and of the springs 35 in particular The armature 28 has anannular flange 38 in which a series of circumferentially spaced holes 39is provided,.into any one of. which a latch 40 projecting irom a hole 4|provided in the rim portion 34 of the pressure plate I1 is arranged tobe entered to lock the armature against turning with respect to thepressure plate. A coiled compression spring 42 fitting in the hole 4| inback of the latch 40 normally urges the same outwardly for engagementwith the flange 38, and when an adjustment is to be made a drift pin isentered in the hole 39- from the back of the clutch to retire the latch40 against the action of its spring so as to allow the armature to beturned. An annular groove 43 is provided in the shank of the latch 40which comes into register with a radial hole 44 provided in'the rim 34when the latch is moved to retracted position, thus permitting thelocking of the latch in retracted position by simply entering a pin inthe groove 43 through the hole 44. The armature can then be adjustedeither by means of. the drift pin entered in the hole 39, or another pinset into any one of a plurality of radial holes 39' provided in the rimof the armature. approximately .004" in advancing the latch 40 one hole.Manifestiy, as wear of the friction faces occurs, the air gap 31 uponengagement of the clutch is proportionately diminished, and it is,therefore, necessary to back the armature away from the magnet bythreaded adjustment thereof. relative to the pressure plate tocompensate for the wear. Due to the threaded adjustment there is nodanger of disturbing the parallelism between the magnet and armature. Inother clutch constructions involving the use of plural point adjustmentsit was an extremely difficult matter to make an adjustment withoutthrowing the armature and magnet out of parallelism, and, naturally, ifthese parts are not truly parallel, the air gap therebetween will not beuniform and the clutch'engagement will accordingly lose its uniformity,with the result that the clutch will not transmit power properly andwill wear unevenly. Naturally, too, a single adjustment can be made in asmall fraction of the time required for the other adjustments.

Since the size of the air gap is so important, I have provided two waysof checking same; One is by means of a plunger 45 mounted in a plug 46in the armature 28 and normally held in engagement with the face .of themagnet 24 under the action of a coiled compression spring 31 provided inthe plug fitting about the stem 48 of the plunger. The magnet andarmature turn together, and the plungers 45, of which one or more willbe provided, and equally clrcumferentially spaced if a plurality areused, serve by engagement with the magnet to indicate at all times thesize of the air gap therebetween. The stem 48 is of such length thatwhen the armature is properly adjusted and the clutch is engaged, theouter end thereof. is exactly flush with the face of the plug 46. Inthat way the operator can tellrat a glance and without making anymeasurement whether or not there is the proper air gap. Naturally, ifthe ends of the stems project slightly, it indicates that the frictionfaces have worn to that extent and the armature will have to beaccordingly adjusted to bring back the flush relationship mentioned.Another way of checking th, air gap is by entering a gauging feelerdirectly into said gap through radial slots 49 provided in the rim ofthe armature 28.

In order to prevent overheating of the clutch A very fine adjustment canbe secured ofinasmuch as overheating of these parts would destroy theirtension, I have provided a simple, though effective, ventilating means.Thus, the

- web of the flywheel I has radial slots 50 cored therein, the sides ofwhich are inclined at an acute angle with respect to the plane ofrotationv of the flywheel to serve as fan blades which, in the turningof the flywheel in the direction indicated by the arrow in Fig. 3, causeair to be taken in as indicated. by the small arrow in Figure 1. Holes5| provided in the front plate i3 register with holes 52 provided in thedriven discs l6 and holes 53 in the pressure plate l1, and the air takenin through the slots 50 flows through these registering holes andthrough radial slots 54 provided in the rim portion 34 of the pressureplate, as indicated by the small arrows. The holes 5l.53 are concentricwith the recesses 36 in which the spring 35 are seated and hence the airin flowing from the slots 50 through the clutch to the slots 54 servesto keep the springs cool besides ventilating the clutch as a whole. Theair taken in through the slots 50 should tend to assist materially inthe clearing out of any worn off friction material from between thedriving and driven discs when the clutch is disengaged and the discsmove apart.

It is believed the foregoing description conveys a good understanding ofall of the objects and advantages of my invention. The appended claimshave been drawn with a view to covering all legitimate modifications andadaptations.

I claim:

1. In a clutch, the combination of driving and driven shafts, a drivingelement on the driving shaft, a driven element on the driven shaft,friction drive discs on one of said elements and arranged tofrictionally engage friction drive discs on the other element tointerconnect said elements, a pressure plate movable on butnon-rotatable with respect to one of said elements and arranged to causeengagement of said discs, an annular magnet fixed on and turning withthe same element and arranged to be energized, an

annular armature rotatable relative to the pressure plate and adjustablythreaded on a part projecting from the pressure plate and disposed inclose relation to the magnet so as to be attracted.

thereby, the threaded connection and rotatability of the armaturerelative to the pressure plate permitting adjustment of the armaturerelative to the magnet to compensate for wear of the aforesaid discs,and spring means for normally tending to move the pressure plate toretracted position, whereby to move the armature away from the magnet.

2. In a clutch, the combination of driving and driven shafts, a drivingelement on the driving shaft, a driven element on the driven shaft,friction drive discs carried on one of said elements and arranged toengage friction drive discs on the other element to transmit drivethereto, a pressure plate for causing engagement ofv said discs. thesame being non-rotatably mounted on one of said elements but movabletoward and away from the discs, an annular magnet carried on the sameelement with the pressure plate, an annular armature slidabl'y and.rotatably mounted on said element in juxtaposition to the magnet so asto be attractedthereby, said armature being threaded on the pressureplate to permit adjustment relative to the magnet when the armature isturned relative to the pressure plate,

whereby to maintain a predetermined air gap between the magnet andarmature when the pressure plate is in operative position, spring meanstending to move the pressure plate to retracted position, and meanscooperating with the armature to limit its retracting movement wherebyto keep the same a certain distance from the magnet when the pressureplate is in retracted position.

3. In a magnetic clutch, the combination of a revoluble hub, an annularmagnet stationarily mounted on and turning with the hub, a driving and adriven shaft, one of said shafts being fixed to the hub, driving anddriven clutch elements for frictionally driving the driven shaft fromthe driving shaft, a non-magnetic part, an annular armature slidablethereon relative to said hub as a guide toward and away from the magnet,

and means operated by the armature in its movement when attracted forfrictionally engaging the clutch elements.

4. In a magnetic, clutch, the combination of a revoluble hub, an annularmagnet stationarily insure a predetermined air gap between the armatureand magnet when the magnet is not energized, an annular pressure platesurrounding thehub on the opposite side of the magnet from the armature,the same serving to frictionally engage the clutch elements underpressure, means providing an operating connection betweenthe armatureand the pressure plate for transmitting pressure to the clutch elementsby the pressure plate upon attraction of the armature, and spring meanstending normally to move the pressure plate and armature to retractedposition, whereby to cause the armature to engage the aforesaidshoulder.

- 5. In a magnetic clutch, the combination of a revoluble hub, anannular magnet 'stationarily mounted on and turning with the hub, adriving and a driven shaft, one of said shafts being fixed t6 the hub,driving and driven clutch elements for frictionally driving thev drivenshaft from the driving shaft, a non-magnetic collar on said hub, anannular armature slidable on said collar. as a guide toward and awayfrom the magnet, the collar having a shoulder limiting movement of thearmature away from the magnet, whereby to insure a predetermined air gapbetween the armature and magnet when the magnet is not energized, anannular pressure plate surrounding the hub on the opposite side of themagnet from the armature, the same serving to frictionally engage theclutch elements under pressure, spring means tending normally to movethe pressure plate and armature to retracted position, whereby to causeengagement of the armature with the aforesaid shoulder, and meansproviding an adjustable threaded operating connection between thepres-"sure plate and the armature whereby to move the pressure platetowardthe front plate upon attraction of the armature and permitadjustment of the pressure plate awayfrom the aforesaid shoulder tocompensate for elements. l I l 6. In a magnetic clutch, th e combinationof a wear of the clutch revoluble hub, an annular magnet stationarilymounted on and turning with the hub, a driving and a driven shaft, oneof said shafts being fixed to the hub, driving and driven clutchelements for frictionally driving the driven shaft from the drivingshaft, an annular armature slidable relative to said hub as a guidetoward and away from the magnet, an annular pressure plate surroundingthe hub on the opposite side of the Y magnet from the armature, the sameserving to determined spaced relation between the armature and themagnet, said last mentioned means being constructed so that at least oneopening is provided affording access to the air gap between the face ofthe magnet and the inside faceof the armature, whereby to permit directmeasurement of said gap.

'7. A clutch of the class described comprising in combination with anannular magnet, an annular armature turning therewith and arranged to beattracted thereby, and friction clutch means engaged by movement of thearmatm'e toward the magnet upon attraction, of an air gap indieatingplunger mounted on the armature for unlimited movement in the directionof the magnet, whereby to indicate by constant engagement with themagnet and the position of the plunger relative to the armature, thesizeof the air gap between' the armature and magnet, said plunger havingan outer end arranged to lie flush with a surface on the back of thearmature when the armature is spaced a predetermined distance from themagnet, and spring means normally holding tended from the armature forconstant engagement with the magnet, said plunger being of apredetermined length so as to have the outer end thereof lie flush witha surface on the back of the armature when the armature is spaced aprede-.

ed connection between thearmature and theclutch, whereby to maintainapredetermined air for frictionally driving the driven shaft from the,

driving shaft, an'annular armature slidable relative to saidhub as aguide toward and away from the magnet, an annular pressure platesurrounding the hub on the opposite side of themagnet from the armature,the same serving to fricttionaliy engage the clutch elements underpressure, and annular flanges on the pressure plate.

and armature threadedly engaged to afford an adjustable connectionbetween the armature and pressure plate for transmitting pressure to theclutch elements upon attraction of the armature by the magnet, thethreaded engagement of said flanges permitting adjustment of thearmature relative to the pressure plate to secure a predetermined airgap between the armature and the magnet, the flange on the armaturehaving at least one opening provided therein through which the insideface of the armature is visible from the outside of the clutch so as topermit direct measurement of the air gap.

10. A magnetic clutch comprising a driving and a driven member, aplurality of cooperating friction rings carried by each of said membersand adapted to be forced laterally into' engagement with each other totransmit driving torque from said driving to said driven member, one ofsaid members having an annular channel formed therein, an annularenergizing winding positioned within said annular channel, an armatureadjustably supported by said last mentioned member 25 for varying thetorque transmitted by said magnetic clutch and adapted to be movedtowards said last mentioned member when said winding is energized, saidarmature being spaced from said friction rings, and means fortransmitting the force of said armature to said friction rings, saicti;earmature and said means being slidably actua d.

11. In a magnetic clutch, the combination of 1 a revoluble hub, anannular magnet stationarily the armature to retracted position inengagement with the shoulder,- an annular pressure plate surrounding thehub on the opposite side of the magnet .from the armature and arrangedto move the clutch elements into engagement, and means surrounding thearmature providing an adjustable threaded connection between thepressure plate and armature whereby the pressure plate moves with thearmature.

12. A clutch of the class described comprising in combination with anannular magnet, an annular armature turning therewith and arranged to beattracted thereby, and friction clutch means engaged by movement of thearmature toward the magnet upon attraction, of an air gap indicatingplunger mounted on the armature for unlimited movement in the directionof the magnet, whereby to indicate by constant engagement with themagnet and the position of the plunger relative to the armature, thesize of the air gap between the armature and magnet, and spring meansnormally holding the plunger extended from the armature for constantengagement with the magnet.

13. A magnetic clutch comprising a driving and a driven member, one ofsaid members having an outer shell like portion and the other of saidmembers having a hub like portion located within said shell likeportion, friction means alternately slidably secured to said shell likeportion and said hub like portion, an electromagnet/spaced axially fromsaid friction means and having an annular pole directed outwardly awayfrom said friction means, an armature for said magnet located in frontof said annular pole, a pressure applying element located between saidmagnet and said friction means and operated by said armature, a pressureresisting element located on the other side of said friction means, saidelectro-magnet and said armature and said pressure applying and pressureresisting elements being carried by one of said members, and screwthreaded adjusting means for varying the spacing between the pressureapplying element and the pressure resisting element to compensate forwear of said friction means.

14. In a magnetic clutch, the combination of driving and driven shafts,a driving element on the driving shaft, a driven element on the drivenshaft, friction drive disks mounted on the driving and driven elementsand adapted to be frictionally engaged to transmit drive from thedriving to the driven element, a pressure plate slidably andnonrotatably mounted on one of said driving and driven elements formovement toward and away from said disks to cause engagement thereof, anannular magnet fixed on the element on which the pressure plate ismounted so as to turn therewith, collector rings electrically connectedwith the magnet for energizing the same by passage of currenttherethrough, a collar for supporting said rings having an annularflange of non-magnetic material fitting over the end of the element onwhich the magnet is mounted and serving to support said rings in trueconcentric relation to said member, an annular armature of magneticmaterial movable with said pressure plate and slidably mounted on saidflange for movement toward and away from the magnet, spring meanstending normally to move the pressure plate to retracted position, andan annular shoulder provided on said collar for abutment by the armatureto limit the retracting movement thereof, whereby to hold said armaturein a predetermined spaced relation to the magnet when the pressure plateis in retracted position. t

15. In a magnetic clutch, in combination, a driving and a driven member,a plurality of cooperating friction rings carried by each of saidmembers and adapted to be forced laterally into engagement with eachother to transmit driving torque from said driving to said drivenmember, an electromagnet spaced axially from said friction rings, anarmature for said electromagnet located axially in front thereof, apressure applying element located at one end of said friction rings andapressure resisting element located at the other end thereof, saidpressure applying element being operated by said armature, saidelectromagnet and said armature and said pressure applying and pressureresisting elements being carried by one of said members, and means foradjusting the spacing between the pressure applying element and thepressure resisting ele- -ment to vary the torque of the clutch.

16. A magnetic clutch comprising, in combina, tion, a driving and adriven member, one of said members having an outer shell like portionand the other of said members having a hub like portion located withinsaid shell like portion, cooperating friction rings operating betweensaid shell and hub like portions adapted to be forced into engagementwith each other to transmit ment being operated by said armature, saidelec tromagnet and said armature and said pressure applying and pressureresisting elements being carried by one oi said members, and means foradjusting the spacing between the pressure applying element and thepressureresisting element to vary the torque of the clutch.

EARL BERRY.

